Catalog - Globoquadrina pachyderma pacifica

CATALOG OF ORIGINAL DESCRIPTIONS: Globoquadrina subsp. pachyderma pacifica Boltovskoy & Watanabe 1986

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> G -> Globoquadrina -> Globoquadrina pachyderma pacifica
Other pages this level: G. altispira conica, G. altispira globosa, G. asanoi, G. dehiscens praedehiscens, G. globularis, G. himiensis, G. kagaensis, G. langhiana, G. larmeui, G. obesa, G. pachyderma pacifica, G. palmerae, G. patriciae, G. pozonensis, G. primitiva, G. pseudofoliata, G. quadraria advena, G. sellii, G. subdehiscens, G. tripartita laxispira, G. tripartita tricamerata

Globoquadrina pachyderma pacifica

Citation: Globoquadrina subsp. pachyderma pacifica Boltovskoy & Watanabe 1986
Rank: sub-species
Described on page(s) : 132-133
Type specimens: Plate 1, figures 1-14. Holotype (fig. la-c), FMACN n.o 11101, 13 figured paratypes, FMACN n.o 11102 (figs. 2-14). Not figured paratypes (3.540 specimens), FMACN n.o 11103. Ten specimens were sent to the Foraminiferal Collection of the Smithsonian Institution (Washington, USA).
Type age (chronostrat): Quaternary
Type locality: USNS ELTANIN core 3-5, depth in core 41-793 cm. Location of core: 16 03' S; 76° 46' W; water depth 2835 m. Core 3-6, depth in core 21-1003 cm. Location of core: 16° 01' S; 76° 47' W; water depth 2780 m.
Type repository: Buenos Aires; Foraminiferal Collection of the Museo Argentina de Ciencias Naturales «B. Rivadavia» (FMACN), Buenos Aires, Argentina.

Linked specimens: USNM-446768

Current identification:


Original Description

Test white, small-sized for the genus, trochoid, with a high ri:l.ther loose spire of about three convolutions, all visible on the spiral side, and rour..ded, looulate equatorial periphery; chambers subsphe.rical, up to 15 in the adult test, five, more sudom four or six, in the final whorl, last chalrlber usually umbilically displaced; majority (= 90 %) of the specimens dextral: proloculus diameter about 0.01 mm; wall calcareous, finely perforated, densely pitted, radial in structure. Umbilicus relatlvely small, shallow; sutures distinct, radial on the umbilical side, less so on the spiral side; aperture a distinct arch with (or sometimes without) a lip, umbilical in position.

Size:
Holotype (flgs. la-c): largest diameter 0.20 mm, height of test 0.18 mm. Paratypes: maximum diameter up to 0.3 mm, average 0.21 mm. Maximum height up to 0.25 mm.

Etymology:

Extra details from original publication
Remarks: The general shape (figs. 10, 12), height: breadth ratio (figs. 4, 6) and aperture (figs. la, 14) of this foraminifer show considerable variation. Attempts to distinguish between megalospheric and microspheric forms were not successful. The general morphology of our specimens resembles that of Globigerina lozanoi Colom and can be also related to Globoquadrina pachyderma (Ehrenberg).

A detailed study showed that it is distinguished from the former species by its densely pitted rather than finely reticulated wall and considerably smaller size. In addition, it is found in Quaternary deposits, whereas G. lozanoi was recorded from the lower Eocene of Central America and Cuba. The opinion of Dr. G. Colom, who kindly compared our specimens with his primary types of G. lozanoi, was that they do not belong to the species G. lozanoi (in litt., 2 january, 1985).

Through the kind assistance of Dr. M. Buzas, specimens of this taxon were checked by Drs. N. G. Kipp, F. L. Parker and E. Vincent, who concluded that our organisms are probably phenotypes of Globigerina pachyderma, and that this «very interesting foraminifer », is potentially useful and should be described (N. Kipp, in litt., 15 March, 1985). F. L. Parker suggested that they can be attributed to «G. cf. pachyderma or forma ditto».

It is probably this is not a new species, but we agree with Kipp's opinion in that, due to its unique features (the only Globigerina and Quaternary Globoquadrina with such a high spired form and displaced last chamber), it should be recorded. Calling it «G. cf. pachyderma>  would imply burying it anonymously in the literature among the many foraminifers mentioned under this conditional name. We believe that our specimens fulfill adequately the requirements for a subspecies. It is probable that its peculiar morphology responds to some particular ecological conditions. According to Burkov et al. (1971) the area where cores 3-5 and 3-6 were retrieved is characterized by the following hydrological setting.

Approximately at parallels 17°-18° S there is a boundary between two hydrological structures: The Subtropical Oriental Austral to the north and the Peru-Chilean to the South. The hydrological section of the former consists of the following water masses:
a) From the surface down to 50-75 m: Surface Water. Temperature 17°-20° C; salinity 35.0-35.2%o; oxygen 5.1-5.5 ml/l. Movementnorthward.
b) From 50-75 m down to 400 m: Subtropical Water. Temperature higher than 9° C; salinity 34.7%o; oxigen 0.20-0.25 ml/l. Movement- southward.
c) Below 400 m: Antarctic Intermediate Water. Temperature ~ 5.5° C; salinity 34.5- 34.55%o. Movement-northward.

The Peru-Chilean structure comprises:
a) From the surface down to 80 m: Surface Water. Temperature 16-17° C; oxygen 5.5- 5.6 ml/1. Movement-northward.
b) 80-200 m: Subantarctic Surface Water. Temperature no C; salinity 34.1-34.7%o. Movement- northward.
c) 200-400 m: Subtropical Surface Water. Temperature 8-11 o C; salinity 34.55-34.80%o, oxygen 0.30-0.50 ml/1. Movement-southward .. d) Below 400 m: Antarctic Intermediate Water. Temperature 5.0° C and lower; salinity 34.35-34.50%o. Movement-northward.

These structures lack a permanent and sharp boundary. Relating Globoquadrina pachyderma pacifica n. subsp. to any particular water mass or hydrological phenomenon (as, for example, the El Nino events, cf. suggestion of N. Kipp, in litt.) is impossible until an adequate collection of plankton samples can be examined.

Editors' Notes

References:

Boltovskoy, E. & Watanabe, S. (1986). Globoquadrina pachyderma pacifica, a new subspecies of planktonic foraminifera from the Quaternary of the southeastern Pacific Ocean. Revista Española de Micropaleontología. 18(1): 131-135. gs V O


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Globoquadrina pachyderma pacifica compiled by the pforams@mikrotax project team viewed: 8-8-2022

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